Sulfite Oxidase Deficiency is a rare autosomal recessive metabolic condition, characterized by neurologic defects, such as seizures, multicystic leukoencephalopathy with brain atrophy, generalized dystonia and choreoathetosis, as well as minimal development of language. Approximately 50 cases have been reported with Sulfite Oxidase Deficiency worldwide. There is no treatment for this disease, and it is fatal in infancy or early childhood. Survivors often exhibit profound mental retardation.
Vianey-Liaud et al. (1988) reported an affected child of a consanguineous Algerian couple. The proband, a boy, died at 9 days of life. Two older sibs, a boy and a girl, had died in the first days of life, apparently of the same disorder.
Seidahmed et al, (2005) described a boy born to first cousin parents with isolated sulfite oxidase deficiency. At 2 days of age he presented with refractory generalized seizures. At the age of 6 months he developed some dysmorphic features including a narrow bifrontal diameter, large ears, and deep-seated eyes. Two months later he was found to have microcephaly, lack of visual fixation, global neurodevelopmental retardation, brisk reflexes, truncal hypotonia with spasticity of all limbs, and clonus. Ophthalmic examination showed cortical blindness. A homozygous delG1244 in the SUOX gene was identified in the affected patient, resulting in a frame-shift at amino acid 117, thus generating 12 new codons. Both parents were heterozygous for the same mutation.
Eyaid et al, (2005) reported two siblings, a 1-year-old girl and an 8-year-old boy with isolated sulfite oxidase deficiency. Both children presented with intractable seizures. The affected girl, at four days of age, became inactive with poor sucking and began to have intractable seizures. She was micorcephalic with poor head and trunk control. At the age of one year, she continued to have partially controlled seizures and poor sucking reflex. A novel liquid chromatography tandem mass spectrometry test revealed an abnormal S-sulfocysteinuria level. Her affected brother started to have intractable seizures at five days of age. At the age of eight years, he was severely micorcephalic with spastic quadriplegia and bilateral dislocation of lenses. His S-sulfocysteinuria level was also abnormal. Both siblings had normal xanthine, hypocanthine, and uric acid levels, which is consistent with isolated sulfite oxidase deficiency.
[See also: Sudan > Salih et al., 2013].
Salih et al. (2013) described a consanguineous family followed for eight years with three children with clinically and biochemically defined Sulfite Oxidase Deficiency. Two of the children were genetically confirmed by the presence of a novel SUOX mutation. The first pregnancy for the family resulted in a female child who was aborted therapeutically at five months of gestation because of anencephaly. A second child was also a female who was born prematurely at 24 weeks gestation, developed an intraventricular hemorrhage, and died at two weeks postpartum without a definitive diagnosis. The third child was a girl born at full-term and developed seizures on the second day of life. She became microcephalic with spastic upper and lower extremities and exaggerated deep tendon reflexes. Brain computed tomography (CT) at the age of 11 months showed loss of white matter and white matter cysts mainly in the corona radiata and centrum semiovale, enlarged cerebral sulci and lateral ventricles, faint calcification in the thalami, and massive dilatation of the ventricular system and cisterna magna. Bilateral lens subluxation compatible with Sulfite Oxidase Deficiency was noted, and urinary S-sulphocysteine level was documented to be 326 ?mol/mmol of creatinine (control <10). She died at age 14 months of respiratory complications. The fourth child was healthy until the third day of life, when he developed generalized tonic-clonic seizures, decreased activity, and poor feeding with obviously increased muscle tone. Brain CT at the age of four days showed generalized brain swelling involving supratentorial structures with effacement of cerebral sulci and compression of the bodies of the lateral ventricles with later development of cystic changes in the cerebral hemispheres, white matter loss, enlargement of sulci, and thalamic calcification. Urinary S-sulphocysteine was elevated (144 ?mol/mmol of creatinine) while urinary xanthine and hypoxanthine were normal. At age 10 months he had microcephaly associated with evolving facial dysmorphism, gross motor delay, and diffuse hypotonia with brisk deep tendon reflexes. He remained vegetative and oxygen-dependent at age eight years. The fifth pregnancy was a genetically normal male fetus that aborted at three months gestation after diagnostic chorionic villus sampling performed at 10 weeks. The sixth pregnancy yielded a normal girl, while the seventh child was a boy with biochemically proven Sulfite Oxidase Deficiency who began to seize on the second day of life and died on day 15. The eighth pregnancy was achieved after a successful implementation of preimplantation genetic diagnosis and yielded a normal male child.
Al-Shamsi et al. (2014) undertook a study to calculate the birth prevalence of IEMs among Emiratis in the UAE by taking into consideration all neonates born with an inherited metabolic condition at Tawam Hospital between 1995 and 2012. Sulfite Oxidase deficiency was found to have a birth prevalence of less that 0.98 per 100,000. One novel mutation was identified in the SUOX gene among the affected patients.